Sourdough Hydration Calculator
Enter your flour weight and pick what you want to solve for. If you use a sourdough starter, this calculator breaks it into its own flour and water automatically, using the method taught by King Arthur Baking and the Bread Bakers Guild of America, not the simplified approximation some recipes use instead.
Common hydration targets
Presets assume 500g flour and no starter. Tap one, then enter your real flour weight below.
| Ingredient | Weight |
|---|---|
| Total dough weight | n/a |
| Salt | n/a |
| From your starter | n/a |
How this is calculated
Total hydration is total water divided by total flour, times 100. The part that trips people up is the starter: it isn't a single ingredient, it's already flour and water mixed together. A 100%-hydration starter (equal parts flour and water, the most common kind) splits evenly: 200g of starter is 100g flour and 100g water. A stiffer or wetter starter splits differently, which is what the starter hydration field is for.
The math: starter flour = starter weight ÷ (1 + starter hydration ÷ 100). Starter water = starter weight minus that. Everything else follows from there.
Does your flour need to be stronger at higher hydration?
Above roughly 75-80%, all-purpose flour starts to struggle holding the dough's structure, since it doesn't have enough protein to build the gluten network a wet dough needs. Bread flour, with its higher protein content, handles high hydration far more comfortably. If you're pushing toward the top of the range and the dough feels like it's falling apart rather than just being sticky, the flour is a more likely cause than the technique. See the Flour Substitution Guide for the protein-content reasoning behind that.
Worked example
Take 700g of flour, a 200g starter at 100% hydration, and a 70% target hydration. The starter splits into 100g flour and 100g water. Total flour is 800g. To hit 70% true hydration you need 560g of total water, but 100g of that is already sitting in the starter, so you only add 460g of water. If you'd ignored the starter and just added 700g × 0.70 = 490g of water on top of it, you'd land closer to 590g total water against 800g flour, about 74% instead of 70%. It's not usually a huge miss, but it compounds the more starter a recipe calls for.
Frequently asked questions
How do I calculate sourdough hydration with starter?
What is considered high hydration sourdough?
What's a good hydration percentage for a beginner?
Does starter hydration matter if I always use the same starter?
How this is checked. The hydration formula on this page follows the method King Arthur Baking and the Bread Bakers Guild of America teach for accounting for starter in a dough's total hydration, cross-checked against several independent baking references rather than a single source. It is not the simplified approximation (dividing starter percentage by ten and adding it to the water percentage) that some recipe sites use for quicker mental math. If the underlying convention changes, this page gets rechecked and updated.